Japanese Patent Application Publication Number 2000-252084 A (hereinafter referred to as a “Document 1”) discloses a lighting system configured to produce light environment suitable for a human biological rhythm such as a circadian rhythm or the like all through the day. The lighting system includes a lighting fixture capable of emitting a high illumination light, a middle illumination light and a low illumination light, and a control device configured to perform lighting control of the lighting fixture. The control device performs a lighting control of the lighting fixture, thereby allowing the lighting fixture to emit a high illumination light in a first time slot from morning to almost early-evening. The control device then allows the lighting fixture to emit a middle illumination light in a second time slot from the early-evening to bedtime, where at least average illuminance on a temporal axis of the middle illumination light is lower than a maximum illuminance in the first time slot. The control device further allows the lighting fixture to emit a low illumination light in a third time slot from the bedtime to next morning, where an average illuminance of the low illumination light is lower than a maximum illuminance in the second time slot.
The lighting system of Document 1 is mainly directed to a facility such as a hospital room in which (a) patients stay(s) for an almost whole day from wake time to bedtime. Twenty four hours of a day are divided into three time slots (three periods), namely a time slot from morning to early-evening, a time slot from the early-evening to bedtime, and a time slot from the bedtime to next morning. Illuminances to be secured for the time slots are define as high, middle and low illuminances.
Setting of the time slots and lighting control in each time slot do not take into consideration working hours at a workplace such as an office, a workshop or the like. That is, the lighting control does not take into consideration a biological rhythm in working hours from morning to early-evening or night in particular.
In recent years, energy-saving is desired. It is therefore important to balance the light environment suitable for the biological rhythm with energy-saving in lighting control for working hours.